These types of devices are generally known and in particular described in publication DE 10 200 896 A1. Publication DE 10 200 896 A1 discloses a method for renovating saturated flat roofs, while maintaining their substance, with which a heat insulation plate is either laid directly over the old roof structure or the old covering layer of the old roof structure is removed before it is laid. On their lower side the heat insulation plates have a water-absorbent or -retaining layer which also releases the water again, by means of which it is possible for the damaged flat roof to be dried. In this way, costs associated with a total renovation such as the costs for rebuilding and material, costs for disposing of the old roof material and the heat insulation layers and further building materials, such as for example polyurethane hard foams and extruded polystyrene, are reduced or totally avoided. However, the heat insulation plate disclosed in this document is also very expensive and complex to produce.
Document DE 196 10 450 A1 proposes a method for renovating a flat roof of a reinforced concrete prefabricated garage with which purlins are disposed over the flat roof which have purlin feet by means of which the purlins are attached to the flat roof in need of renovation. A sheet steel second roof is applied over the purlins, and this covers the flat roof with an overhang. Due to the extremely large dimensions with large buildings, the transportation of these second roofs, e.g. to building sites, is very complex and expensive, and so not advantageous. Due to their bulkiness and weight, the fitting of such large individual components is also very difficult.
With flat roofs in several parts designed in this way, there is often the problem of leaks at the connecting points. With the conventional measures, e.g. sealing with bitumen or similar, a repair to the leaky parts is complex and often not very successful.